So far, indications are that this is not the case because the release process has safeguards built in. Statistics from the US Sentencing Commission, as well as interviews with federal public defenders and criminal-justice experts, indicate that federal prisoners who are to be released early are predominantly nonviolent and have good conduct records while in prison. Of the 19,500 drug offenders eligible over the next 30 years to apply for early release, 3,417 have had their sentences reduced as of Monday. Of the 1,500 inmates eligible for immediate release, dozens so far have been let go in the past month.

"There has been no release of a flood of violent criminals," says Michael Nachmanoff, federal public defender for the Eastern District of Virginia. "The people who are being released ... overwhelmingly had cases where there was no violence whatsoever and who were given unduly harsh sentences. And now, their sentences are being reduced by a modest amount."

Critics worry the crime rate, which has already ticked upward, will continue to increase as more prisoners apply for a sentence reduction. The Justice Department, for example, has pointed out that according to the Sentencing Commission's own analysis, nearly 80 percent of the 19,500 who would be eligible for early release had prior criminal records. Of the 1,500 eligible for immediate release, about one-quarter carried a weapon or were with someone who carried a weapon when they were arrested.

"This tells us those who are eligible for early release are very likely to commit another crime," Attorney General Mukasey told the Fraternal Order of Police earlier this year.

The sentence reductions came about because last spring the Sentencing Commission reduced the 100-to-1 crack-cocaine ratio in the guidelines. That ratio was created by a 1986 law that deemed a person convicted of possessing five grams of crack cocaine serve the same mandatory minimum sentence as someone who was caught with 500 grams of powder cocaine.

The result: Crack-cocaine offenders serve sentences up to eight times longer than those sentenced for powder cocaine. Because crack is more often used in minority neighborhoods, African-Americans account for 80 percent of those serving time for crack offenses.

Back in 1986, the 100-to-1 ratio was thought reasonable because crack was believed to be far more addictive and prone to provoking violence. Since then, scientific studies have concluded that crack cocaine and powder cocaine affect the individual the same way and are equally harmful.

In 1995, the Sentencing Commission determined that the violence associated with crack had more to do with the way it was sold on volatile street corners, rather than any inherent difference between crack and powder cocaine. It then recommended to Congress that the mandatory minimum sentences for the two types of cocaine be equalized. But Congress rejected the recommendation. In 1997 and again in 2002, the commission recommended the disparity at least be reduced from 100-to-1 to 5-to-1. Both times Congress refused.

Last spring, the commission voted again to reduce the disparity. This time, Congress did not actively oppose the change, and it went into effect this past fall.

In December, the commission then voted to make the reduction retroactive. That made the 19,500 federal prisoners currently serving crack sentences eligible for early release. The potential average sentence reduction would be a little more than two years.

The Justice Department urged Congress to again override the Sentencing Commission. It warned that retroactivity would add to an increase in crime.

But Congress allowed the commission's decision to stand. In part, that's because a commission analysis of federal crack-cocaine offenders also determined that 90 percent of their cases did not involve violence. Of those 1,500 who would be available for immediate release, the commission said, only 1 percent were deemed "career criminals" and 6 percent "supervisors" of drug rings.

In addition, the commission also required that inmates eligible for a reduced sentence apply to a federal judge. And the US attorney in every district can oppose any sentence reduction if he or she deems the inmate is too dangerous for early release.

"It seems like Mukasey is stoking the flames of fear, and I don't understand why," says Julie Stewart, president of Families Against Mandatory Minimums, which advocates sentencing reform. "All of these people are only eligible for release. They're not guaranteed release. It's up to Mukasey's US attorneys to argue against their release, if they think they're going to go out and wreak havoc."

Mukasey's office says he stands by his earlier comments.

But many criminal-justice experts say the reduction in the disparity is long overdue.

"I would agree, like most people, that the original legislation that created the disparate sentences for crack versus powder was ill conceived," says James Alan Fox, a criminologist at Northeastern University in Boston. "And therefore changes now to remedy mistakes of the past make sense."

The revised guidelines have been structured well, criminal-justice experts say, in that the decision about reducing an inmate's sentence rests with a federal judge.

"In the cases where the retroactive application of the guideline is pretty clear cut, we are getting agreement from the US attorney's office," says Miriam Conrad, federal public defender for Massachusetts and New Hampshire. "There are some cases in which the legal issues are somewhat more complex, and those are ones that it may take a little bit longer to sort out."

Still, some law-enforcement officials remain skeptical. The Fraternal Order of Police credits the tough mandatory minimum sentences with helping to bring about the reduction in crime in the 1990s. If crack-cocaine disparity is unfair, the organization says, then it would be better to increase the penalties for powder cocaine to the level of crack sentences.

"We believe that letting these people out, their presence on the street, will further harden that trend upward in the crime rate," says James Pasco, executive director of the Fraternal Order of Police.

Professor Fox agrees that there is concern about releasing a large number of crack-cocaine offenders, particularly because many of those eligible for early release now are from a generation that struggled with high levels of criminality in the '80s and early '90s. But they all will be released eventually, he notes.

"Under the logic that we shouldn't let them out because they may reoffend, well, that's true today, may be true tomorrow, and a decade from now," he says. "We have not done much in the meantime to ensure there's positive change when people are in prison."